This paper presents PM
10 fugitive
dust emission factors for a range of vehicles types
and examines the influence of vehicle
and wake characteristics on the strength of emissions from an
unpaved road. Vertical profile measurements of mass concentration of the passing plumes were carried out using a series of 3 instrumented towers. PM
10 emission fluxes at each tower were calculated from knowledge of the vertical mass concentration profile, the ambient wind speed
and direction,
and the time the plume took to pass the towers. The emission factors showed a strong linear dependence on speed
and vehicle weight. Emission factors (EF=grams of PM
10 emitted per vehicle kilometer traveled) ranged from approximately EF=0.8×(km h
−1) for a light (
1200 kg) passenger car to EF=48×(km h
−1) for large military vehicles (
18 000 kg). In comparison to emission estimates derived using US EPA AP-42 methods the measured emission factors indicate larger than estimated contributions for speeds generally>10–20 km h
−1 and for vehicle weights>3000 kg. The size of a wake created by a vehicle was observed to be dependent on the size of the vehicle, increasing roughly linearly with vehicle height. Injection height of the
dust plume is least important to long-range transport of PM
10 under unstable conditions
and most important under stable atmospheric conditions.